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Can fibre prevent colon cancer in men?

There are a number of diseases that can impair the normal functioning of the colon. For men, the most concerning is colon cancer.

According to Bowel Cancer Australia (2018), around 55% of all Australians diagnosed with bowel cancer are men.7

Why are men more frequently affected?

Historically, the significantly higher incidence in men has been attributed to higher rates of smoking and more dangerous working conditions.8

More recently, research has determined the disparity of incidence is likely due to differences in DNA.

According to a 2016 study, the additional X chromosome carried by females is able to function normally and act as protection against rapidly changing cells.8

Following this theory, females would require both X chromosomes to mutate in order to turn cancerous, while males would only require a mutation in the one.8

Can dietary changes prevent colon cancer?

There are a number of modifiable and non-modifiable risk factors that can influence the development of colon cancer.7

Notably, one of these modifiable risk factors is dietary behaviours, which should be of no surprise since, besides housing the majority of our body’s bacterial flora, the key role of the colon is food digestion.

Specifically, a diet that lacks in fibre is strongly correlated to diseases of the colon and the gastrointestinal tract.1,3,4,7

In fact, this inverse association prompted the World Cancer Research Fund to update their consensus on a low-fibre diet significantly increasing risk of colon cancer from ‘probable’ to ‘convincing’.3

What is fibre?

Fibre is a type of carbohydrate. There are two types of fibre, with most plant foods containing some of each kind.

Soluble fibre is found in foods such as legumes, fruits, oats, nuts and seeds, and vegetables.

As suggested, soluble fibre is able to absorb water, which transforms it into a thick gel-like substance in the gastrointestinal tract and helps to soften stools so they can move more easily.5,6

Insoluble fibre is found in the skin of fruits and vegetables, nuts and seeds, whole grains and wheat bran.

Insoluble fibre does not dissolve in water and instead it passes through the gastrointestinal tract relatively intact.

As it remains undigested, it absorbs fluids and other byproducts, which may include potential carcinogens.4,6 This further adds to the stool bulk and speeds up the movement and processing of waste.

While the exact protective mechanism of fibre is unclear, there are a number of potential contributors — one being the combination of consuming both soluble and insoluble fibre, which softens stools and decreases transit time respectively.

This process is potentially protective as there is less contact time between potential carcinogens and mucosal cells.4

Another possibility is that the protective behaviour of fibre may be linked to its fermentation process.

Fermentation within the gut synthesises short-chain fatty acids, in particular butyrate which is known to be important for gastrointestinal health.1,3,4,6

In addition to limiting DNA damage due to oxidation, butyrate is believed to suppress tumor proliferation, reduce inflammation and assist in maintaining the protective barrier in the gut lining.2,4

Despite the protective properties of a high-fibre diet, our typical ‘Western Diet’ encourages low-fibre eating behaviours, which has ultimately resulted in fibre being labeled a nutrient of concern in Australian diets.6

Dietary recommendations

According to the Australian Dietary Guidelines, adult males should be recommended to consume at least 38g of fibre per day, yet in the most recent NNPAS survey, Australian adult males are failing to meet this target.6

Simple recommendations to increase fibre intake:

●        Consume fruit and vegetables daily (with the skin on).

●        Choose wholegrain breads, crackers, cereals, rice and pastas.

●        Incorporate legumes into meals.

●        Sprinkle nuts and seeds over salads and pastas.

●        Choose whole foods, rather than blended or juiced foods.

Pharmacies are able to offer high-fibre supplements to assist in boosting fibre consumption. These supplements are appropriate to recommend to patients struggling to reach their fibre intake through diet alone.

Even so, research has consistently shown that the problem doesn’t appear to be as simple as introducing more fibre into a diet, but rather replacing existing foods with high-fibre alternatives.2,4,5,6

When recommending high-fibre foods and alternatives, patients should not be encouraged to introduce too much fibre too quickly, as this can promote discomfort through intestinal gas, cramping and abdominal bloating.5,6

Recommendations should encourage gradual introduction of fibre over the course of a few weeks along with a corresponding increase in water consumption.

Conclusion

There are a range of nutrition recommendations that can be helpful in preventing the development of colon cancer; however, there is strong research indicating increasing fibre intake is a good place to start, particularly for men.3,4

Individuals concerned about their risk of developing colon cancer should be encouraged to seek consultation from a multi-disciplinary team, including physicians, specialists and dietitians.


Bridget Scrogings, Accredited Practising Dietitian

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